(i) Technical Field
A certain aspect of the embodiments discussed herein is related to a manufacturing method of a semiconductor device.
(ii) Related Art
A mask, in which NiCri (nickel chrome), Au (gold) and Ni (nickel) are layered from a substrate side, is used as an etching mask in a forming process of a via hole of GaN (gallium nitride)—FET (Field Effect Transistor). With the method, fluorine-based gas (for example SF6) of an etching gas and Ni of the etching mask are mixed with each other. As a result, Ni fluoride is left on a sidewall of the via hole as a residue. Japanese Patent Application Publication No. 2008-98456 (herein after referred to as Document 1) discloses a method of using a Cu (copper) mask as the etching mask instead of the Ni mask.
However, with an art of Document 1, Cu may cause contamination of semiconductor. This may result in device property degradation, reliability degradation or the like.